1. Field of the Invention
This invention relates to a method of accessing data recorded in concentric circular or spiral information tracks on a disc in a recorded information reproduction apparatus.
2. Description of the Prior Art
Conventionally, a general approach to get objective address data recorded on a disc such as video disc, compact disc, and CD-ROM disc has been such that the reproduction apparatus coarsely moves a data pickup to be in the vicinity of the objective data by a traverse mechanism, then finely controls a head actuator or a lens actuator of the pickup itself to detect a track containing the objective address data, and sequentially reads address data until detecting the objective address data. In other words, after the track containing the objective data has been detected, it is necessary to wait for arrival of the objective data by rotation of the disc itself. This rotation awaiting time is about 0.3 seconds at the maximum in the case of a compact disc or a CD-ROM disc, which is a big problem.
For example, Japanese Laid-Open Patent Application No. 55-55443 aims at high-speed accessing but is only intended to access the objective track at high speed as described above.
In this case, assume that a data on the outermost track on a disc is accessed when the pickup is on the innermost track. It is relatively easy to reduce to about 0.1 seconds the time taken for detecting the outermost track on which the objective data exists. However, the waiting time after the outermost track has been detected is about 0.3 seconds at the maximum. In this case, the access time for the objective data is 0.4 seconds in total and it is difficult to reduce the time further. The maximum rotation awaiting time is a constant value of about 0.3 seconds which occupies most of the access time.